Mechanisms of Deposit Formation in Internal Combustion Engines and Heat Exchangers

Lepperhoff, Gerhard; Houben, Michaël

doi:10.4271/931032

Cited by 78 publications

(52 citation statements)

References 6 publications

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“…Further fuel expanding out of the nozzle holes is adsorbed in this sooty deposit and reacts to further increase deposit formation rate." This mechanism is supported by investigations shown in [42]. …”

Section: Possible Physical Mechanismsupporting

confidence: 76%

“…Deposition in oxygenated hydrocarbon systems above 250-300°C is dominated by thermal condensation and cracking reactions" [41]. In [42] by G. Lepperhoff and M. Houben it is stated that "Deposit locations at high temperature areas of an engine primarily result from non-metallic residuals from evaporating or burning fuel and/or lubricants".…”

Section: Influence Of Temperature and Chemical Reactionsmentioning

confidence: 99%

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Deposit Formation in the Holes of Diesel Injector Nozzles: A Critical Review

Birgel¹,

Ladommatos²,

Aleiferis³

et al. 2008

SAE Technical Paper Series

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Current developments in fuels and emissions regulations are resulting in increasingly severe operating environment for the injection system. Formation of deposits within the holes of the injector nozzle or on the outside of the injector tip may have an adverse effect on overall system performance. This paper provides a critical review of the current understanding of the main factors affecting deposit formation.Two main types of engine test cycles, which attempt to simulate field conditions, are described in the literature. The first type involves cycling between high and low load. The second involves steady state operation at constant speed either at medium or high load.

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Section: Possible Physical Mechanismsupporting

confidence: 76%

Section: Influence Of Temperature and Chemical Reactionsmentioning

confidence: 99%

Deposit Formation in the Holes of Diesel Injector Nozzles: A Critical Review

Birgel¹,

Ladommatos²,

Aleiferis³

et al. 2008

SAE Technical Paper Series

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show abstract

“…This reduction in performance is known to manifest in a variety of ways including increased acoustic and pollutant emissions [1][2][3]. The deposits can also reduce the hydraulic diameter of the nozzle hole, resulting in a reduction in the quantity of injected fuel and reduced quality and consistency of injection [3][4][5]; all of which cause a reduction in engine power [6]. The deposits can also increase cavitation, which can then lead to further coking of the nozzle [7].…”

Section: Introductionmentioning

confidence: 99%

A quantitative analysis of nozzle surface bound fuel for diesel injectors

Turner

Sykes

Sercey

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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In a fuel injector at the end of the injection, the needle descent and the rapid pressure drop in the nozzle leads to discharge of large, slow-moving liquid structures. This unwanted discharge is often referred as fuel 'dribble' and results in near-nozzle surface wetting, creating fuel-rich regions that are believed to contribute to unburnt hydrocarbon emissions. Subsequent fluid overspill occurs during the pressure drop in the expansion stroke when residual fluid inside the nozzle is displaced by the expansion of trapped gases as the pressure through the orifices is equalised, leading to further surface wetting. There have been several recent advancements in the characterisation of these near nozzle fluid processes, yet there is a lack of quantitative data relating the operating conditions and hardware parameters to the quantity of overspill and surface-bound fuel. In this study, methods for quantifying nozzle tip wetting after the end of injection were developed, to gain a better understanding of the underlying processes and to study the influence of engine operating conditions. A high-speed camera with a longdistance microscope was used to visualise fluid behaviour at the microscopic scale during, and after, the end of injection. In order to measure the nozzle tip temperature, a production injector was used which was instrumented with a type K thermocouple near one of the orifices. Image post-processing techniques were developed to track both the initial fuel coverage area on the nozzle surface, as well as the temporal evolution and spreading rate of surface-bound fluid. The conclusion presents an analysis of the area of fuel coverage and the rate of spreading and how these depend on injection pressure, in-cylinder pressure and in-cylinder temperature. It was observed that for this VCO injector, the rate of spreading correlates with the initial area of fuel coverage measured after the end of injection, suggesting that the main mechanism for nozzle wetting is through the impingement of dribble onto the nozzle. However, occasional observations of the expansion of orifice-trapped gas were made that lead to a significant increase in nozzle wetting. KeywordsDiesel; end of injection; dribble; surface wetting; image processing Introduction Increasingly strict emissions standards place considerable pressure on the automotive industry to increase the efficiency of, and reduce the emissions of the engine. This is primarily done by optimising the fuel-air mixing processes that occur inside the combustion chamber. Since the fuel air mixing is affected by the fuel injection equipment (FIE), much of the research efforts have been in improving the injector design and spray characteristics. This has resulted in the numbers of holes in the injector tip increasing with subsequent designs, as well as increases in the operating pressure, with typical systems operating with common rail pressures of over 200 MPa. These increasingly harsh conditions are believed to accelerate the formation and growth of deposits in and arou...

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“…This erosion process, described by Epstein [19], has not received adequate attention. Removal processes include mechanisms such as turbulent bursts, impacts, rolling, and scrubbing actions and have been proposed to be strongly linked to velocity [20].…”

Section: Introductionmentioning

confidence: 99%

Experimental study of soot particle fouling on ribbed plates: Applicability of the critical local wall shear stress criterion

Paz

Suárez

Concheiro

et al. 2013

Experimental Thermal and Fluid Science

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This article examines the notion of critical wall shear stress as the key control parameter of the local fouling removal process. In this study, an experimental setup was developed for measuring fouling on enhanced surfaces. Specifically, the experimental configuration consists of a forced convection plate heat exchanger containing a one-pass rectangular channel with two ribbed plates arranged in a symmetrically staggered manner. The exhaust gases flow by the rib-roughened sides of the plates, and the flat sides can be cooled with water from the independent external coolant circuit.As a result of soot particle deposition from exhaust gases, a layer of fouling is deposited over the ribs.After asymptotic conditions were reached during the tests, detailed fouling thickness measurements were conducted. The dimensionless particle relaxation time during these tests was determined to be in the range of 0.3-10. The measurements were then complemented with a numerical analysis. In particular, the local wall shear stress was calculated using a commercial computational fluid dynamics (CFD) software package.The fouling thickness profiles deposited over the ribs and the local critical shear stress values were compared and discussed for two different geometries. The results obtained clearly support the idea that critical wall shear stress is an appropriate criterion for facilitating the understanding of the local behaviour of fouling deposits.

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Mechanisms of Deposit Formation in Internal Combustion Engines and Heat Exchangers

Cited by 78 publications

References 6 publications

Deposit Formation in the Holes of Diesel Injector Nozzles: A Critical Review

Deposit Formation in the Holes of Diesel Injector Nozzles: A Critical Review

A quantitative analysis of nozzle surface bound fuel for diesel injectors

Experimental study of soot particle fouling on ribbed plates: Applicability of the critical local wall shear stress criterion

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